Reflex copying by diffusion transfer



Dec. 7, 1965 A E. H. LAND I 3,222,171

REFLEX COPYING BY DIFFUSION TRANSFER Filed my 21. 1961 I ACTINIC LIGHT leb Developable Silver HaIIde Original *40 IBC IBG IBC LlghI Area of Original (Reflecf'inq) I' Developable Silver Halide Durk Area of Original (Non'Reflecfing) PREAD PROCESSING FLUID I4\ (IBC |601 Mw IBC) (I4 [l2 W/lb ///f44 /A/Imuqe Supporf' Shed- 42/ *Diffusion Transfer Silver Image STRIP FIG.

...mi Huur-u nu.. ,I Fluid Lay" 44 poum. 26mm 1mg.

S f 20 {fslfg fil/4 Emulsion Phofosensif'ive Shee-I .L-VSuppor'I' c OI-ETOR' wvEmulsion BY 4MM/MW TORNEYS United States Patent O 3 222 i371 REFLEX COPYING BY nrErUsloN TRANSFER Edwin H. Land, Cambridge, Mass., assigner to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed July 21, 1961, Ser. No. 125,855 6 Claims. (Cl. 96--29) This application is a continuation-impart of my copending U.S. application Serial No. 666,148, filed June 17, 1957, entitled Method of Reex Copying and Product Useful Therein (now abandoned).

This invention relates to photography and, more particularly, to a novel method of reflex copying and products useful therein.

A Well-known method of making copies, particularly of documents `and printed matter, is known as reflex copying or printing by contact in reflected light, and involves superposing a sheet of photosensitive material with the surface of a subject (document) to be copied and directing actinic light through the photosensitive material to the subject where the light is absorbed by the dark areas f the subject and returned `from the light areas, differentially exposing the photosensitive material to produce a developable image therein. Conventional reflex copying processes require the use of very high contrast photosensitive materials, usually silver halide emulsions, and accordingly suffer from a number of serious limitations or drawbacks inherent in the use of emulsions having very narrow contrast and density ranges. Among these drawbacks inherent in the use of such emulsions are the fact that it is virtually impossible to reproduce differences in tonal values so that conventional reex copying methods cannot be employed for copying matter such as photographic prints to give `continuous tone copies, and there is afforded practically no latitude in controlling exposure time.

Objects of the invention are: to provide a novel method of reflex copying having substantial exposure latitude considerably greater than is possible with prior art reflex printing methods and which may nearly approximate the exposure latitude of contact printing by transmitted light; to provide a reflex copying method which may be utilized for reproducing intermediate tones as well as blacks; to provide a method as described which includes the formation of a positive transfer image of the subject being copied from a photosensitive material, exposure of which is restricted substantially to light reflected from the subject being copied; and to provide novel photographic products useful in said method.

Other objects of the invention are: to provide a method of producing reflex copies utilizing a photosensitive element including a photosensitive layer comprising, as the photosensitive material thereof, a heavy metal salt such as silver halide, which method involves directing light actinic to `the photosensitve material onto and through the .photosensitive element to the surface of the subject with which the photosensitive element is superposed with the photosensitive layer in contact with said surface while, at the same time, preventing substantial exposure of minute areas of said photosensitive layer arranged in a screen pattern, and which in aggregate constitute a substantial portion of an area of the photosensitive sheet substantially coextensive with the area of the subject being copied, and forming a positive image corresponding to the subject by transfer of image-forming substances produced in undeveloped areas of said photosensitive layer by development of a latent image in said layer; to provide a method as described wherein substantial exposure of said minute areas of the photosensitive layer is prevented Iby directing said actinic light through a screen 3,222,171 Patented Dec. 7, 1965 having minute areas which are, by virtue of their composition, substantially impervious to said actinic light; and to provide a method as described wherein said diffusiontransfer includes a predetermined lateral, as well as depth- Wise, diffusion of image-forming substances from unexposed and undeveloped areas of said photosensitive layer and produced therein as a function of the development of said exposed areas.

A further object of the invention is to provide a novel photosensitive element useful in reflex copying including a light-transmitting support sheet, a photosensitive layer and a photographic screen between said support and photosensitive layer having minute areas substantially impervious to light within a predetermined wave length range actinic to the photosensitive material comprising said photosensitive layer.

Other objects of the invention will in .part be obvious and will in apart appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

FIGURE 1 is three enlarged, diagrammatic, fragmentary, sectional views of .photographic products used in the method of the invention and illustrating three steps in said method; and

FIGS. 2 and 3 are enlarged, diagrammatic, fragmentary, sectional views of other forms of products useful in the method of the invention.

The present invention comprehends a novel method of reflex copying having the advantages of substantially greater exposure latitude than methods known heretofore, together with the ability to reproduce tone. Generally, this method involves limiting the reflex exposure of Va layer of photosensitive material such as a photosensitive heavy metal salt, preferably silver halide, to only those areas of the photosensitive material from which an image is to be formed by diffusion-transfer, and then subjecting the exposed photosensitive material to a diffusion-transfer processing to effect the formation of a positive print or copy of the original. The exposure is effected as described by interposing a screen, having minute areas capable of preventing the transmission of actinic light, between the source of actinic light and the photosensitive material which comprises a layer located in superposition with the surface of the original being copied. The transfer processing is then effected preferably by superposing the photosensitive layer with another surface and distributing a fluid processing reagent in a thin layer therebetween, and in the case of silver halide involves the development of the exposed silver halide and the formation, as a result of said development, of transferable image-forming substances. The claimed method may possess the added virtue of being substantially a dry process, the liquid being confined at all times between a photosensitive sheet and another element which is superposed therewith during processing and which preferably comprises a sheet providing a support for the finished positive copy.

In conventional refiex printing methods a photosensitive sheet, usually including a photosensitive silver halide layer carried on a light-transmitting support, is superposed with the surface of a subject, usually a document, printed page, or line drawing to be copied, with the photoseneitive silver halide layer in actual contact with, or in very close proximity to, the surface to be copied. Actinic light is directed through the support of the photosensitive sheet and the photosensitive material to the surface of the subject and the photosentitive material receives a differential exposure by virtue of light reflected from the light or reflective areas of the surface of the subject. The emulsions used in conventional reflex printing are very slow orthochromatic emulsions, very contrasty, and have a very small toe to the characteristic curve. The light which passes through the photosensitive sheet the first time to reach the document is insufficient to produce a latent or developable image, but only a sub-latent image. The light reflected by the light portions of the document, however, has an additive or augmenting effect upon the initial exposure by the incident light and thus forms a rdevelopable image. Since the entire photosensitive sheet is exposed by actinic light and receives only relatively minute differences in exposure, the photosensitive material is required to be very contrasty and the process has very little exposure latitude. A positive copy can be, and usually is, made from the exposed photosensitive silver halide by any of the conventional methods, including silver-transfer processes. Attempts have been made at rellex copying employing diaz-o type materials and utilizing screens or other means for subdividing the illumination which traverses the printing materials. Such processes, however, have proven, at best, to be poorly operative and produce results that are, for the most part, unsatisfactory.

The method of the invention may also utilize a silver halide diffusion-transfer reversal process to forrn a positive print or copy from the exposed silver halide layer, but differs considerably from conventional processes in that exposure of the silver halide or other photosensitive material is controlled so that the photosensitive areas corresponding to openings in the screen are fully exposed by the incident actinic light, while the transfer imageforming areas thereof are restricted to being substantially exposed only by actinic light reflected from the original and are not exposed to any substantial extent by light directly incident from this light source; and the diffusiontransfer processing is also performed in a special manner in order to obtain a positive copy having substantially clean whites, complete blacks and in which tones are also reproduced.

As previously noted, incident exposure is limited by a screen or stencil or the like having areas substantially impervious or opaque to the actinic light used for exposure, said screen being located between the light source and the photosensitive material, and preferably in contact with the photosensitive material. The screen, which may be lined or of any other regular and conventional pattern, includes actinic light-impervious and light-transmitting areas of submacroscopic dimensions such as to be visually indistinguishable, and may comprise, for example, 150 or more lines per inch. The light-impervious areas of the screen comprise a major portion of the photosensitive sheet, ranging between a quarter and threequarters of the total area with the open or light-transmitting areas preferably comprising the remainder of the area. Actinic light passing through the opening in, or the light-previous areas of, the screen irradiates any photosensitive material underlying these openings or areas to the extent that such areas are rendered fully developable and there is substantially no transfer of image-forming substances from these areas of the photosensitive material. Where the openings or light-transmitting areas overlie light-reflecting areas of the original, light difusely reflected from the original acts to expose the photosensitive material underlying adjacent light-impervious areas of the screen in proportion to the reflectivity of the area of the original underlying the screen opening.

Clean whites and complete blacks are obtained in appropriate areas of a transfer print by virtue of a diffusiontransfer process which is controlled so that there is lateral, as well as depthwise, diffusion from the layer containing the photosensitive material. In this manner, the imageforming substance, which may be a dye or the metal of a photosensitive salt such as silver, is deposited in the black areas of the copy underlying openings in the screen (and exposed areas of the photosensitive material) by diffusion from the unexposed photosensitive material underlying actinic light-impermeable areas of the screen. Clean white areas of the positive print are obtained by virtue of the fact that no image can be formed from areas of photosensitive material located in alignment with openings in the screen, nor from areas of photosensitive material underlying actinic light-impervious areas of the screen and exposed by rellected light. Tones are reproduced in the copy by virtue of the fact that the imageforming substance is transferred in proportion to the exposure given to arcas of photosensitive material underlying the actinic light-impervious areas of the screen and this transfer occurs laterally as well as depthwise, so that the tone is reproduced in the areas of the print underlying openings in the screen (and hence containing fully exposed photosensitive material) as well as those areas underlying actinic light-impervious areas of the screen.

The method of the invention is illustrated by the schematic views of FIG. l wherein the thicknesses of the materials employed are shown as being exaggerated for clarity of illustration. The method involves exposure of a photosensitive sheet which basically comprises a support, a screen and a photosensitive silver halide layer. The photosensitive sheet may take a variety of different forms and comprises a number of alternative materials and combinations. In the form shown in FIG. l, for example, the photosensitive sheet, designated 10, comprises a support sheet 12 which is required to be light-transmitting and may be transparent or translucent. Materials suitable for use as support sheet 12 are any of the conventional lm base materials including glass, organic plastic materials, paper and the like.

The photosensitive sheet includes a screen having minute areas or elements arranged in a screen pattern which are substantially impervious or opaque to the light actinic to the photosensitive material comprising said sheet and used for exposing said sheet, and other minute areas arranged in a screen pattern between the light-impervious areas or screen elements for transmitting the actinic light used. The screen need not be opaque to all actinic light, but only to light in the actinic wave length range employed for exposure of the photosensitive material. Such screens are well known in the art and may comprise any desired pattern such as lines or a mosaic of regular pattern, including light-transmitting and opaque areas having dimensions such that individual areas or elements are visually indistinguishable. The expression light-impervious and the term opaque are used herein with particular reference to the transmissibility of light in predermined wave length ranges to which the light-sensitive matcrial comprising the photosensitive sheet is sensitive. Materials are useful for light-impervious or opaque screen elements because of their ability to reect or absorb actinic light while at the same time such materials, referred to as impervious or opaque to actinic light, may transmit light of other wave length ranges.

A form of screen shown in FIG. 1 comprises a multiplicity of line screen elements 14 having submacroscopic width dimensions and spaced from one another by similarly minute distances. For example, these dimensions may vary from as small as is practicable up to several thousandths of an inch within the submacroscopic range, and the dimensions of the screen elements may range from one-quarter of the width of the spaces therebetween to four times the width of the spaces. The light-impervious screen elements may be formed by a variety of known methods and may be impervious by virtue of their ability either to reflect or absorb actinic light. For example, the

screen elements 14 of photosensitive sheet 10 are deposited in depressions or recesses 16 formed in a surface of support 12, as by embossing or molding. This type of screen can be easily produced by known methods including doctoring a fluid vehicle, adapted to solidify and containing a suitable dye or pigment, into recesses 16 where it is allowed to harden. Photosensitive sheet includes a continuous photosensitive layer 18, preferably comprising a photosensitive silver halide emulsion, formed by conventional methods and covering the screen elements. Another embodiment of a photosensitive sheet useful in the method of the invention is shown at 20 in FIG. 2 and comprises a support 22 on one surface of which are provided screen elements 24. A layer 26 containing photosensitive silver halide is provided on the surface of each of the screen elements. Photosensitive sheet 20 can be produced by a number of known methods including, for example, coating the support with continuous layers yof the screen material and the photosensitive silver halide, and then removing portions of the silver halide and the screen layer to provide screen elements and discrete photosensitive layers; or by applying the screen elements to the support by conventional photographic printing or coating methods and then applying the photosensitive material only to the screen elements. Still another embodiment of a photosensitive element useful in the invention is shown at 30 in FIG. 3 and comprises a light-transmitting support sheet 32 dyed in predetermined areas to provide screen elements 34 and coated on one surface with a layer 36 containing the photosensitive silver halide.

The rst step in the process of the invention involves superposing photosensitive sheet 10 with the surface of an original or subject, designated 40, to be copied, with photosensitive layer 18' and the original in contact with one another. Actinic light from a suitable source is directed uniformly through suppolt 12 between screen elements 14 to the subject, thereby exposing any photosensitive material located in the areas between screen elements or opposite openings (non-opaque areas) of the screen, and rendering the silver halide in these areas, designated 18a, developable. For purposes of illustration, the original in FIG. 1 is shown as comprising a sheetlike element having a surface with a dark or nonreecting area and a light or reflecting area. Light passing between the screen elements and incident on the dark area is absorbed and light incident on the light areas of the original is diffusely reflected, thereby exposing areas of the photosensitive layer underlying the screen elements, rendering the silver halide in these areas, designated 18b, developable. The silver halide located in areas 18C iof the photosensitive layer located behind the screen elements between the latter and dark areas of the original remains unexposed and substantially undevelopable.

Photosensitive sheets 20 and 30, shown respectively in FIGS. 2 and 3, are exposed in the same manner as sheet 10. The subsequent processing of sheet 20 differs from that of sheets 10 and 30 only in that there is no photosensitive material located opposite the openings in the screen (between screen elements). However, such material in areas 18a of layer 18 is exposed by incident light and does not enter into subsequent processing insofar as formation of a positive transfer image is concerned. The next steps in the method of the invention involve superposing the exposed photosensitive sheet with a second or image support sheet 42 and distributing `a fluid processing reagent in a thin layer 44 between the photosensitive silver halide layer and the second sheet to effect the development of exposed silver halide and the imagewise transfer of image-forming substances produced as a result of development of the silver halide. While sheet 42 may merely function to aid in spreading and confining the iiuid processing reagent, it is preferably adapted to serve as a support for a positive transfer print and may be formed of any of the materials usually employed as a support for positive prints, such as paper, organic plastics,

6 glass and, in fact, any other material the surface of which can be treated or provided with ay coating for receiving and supporting irnage-forrning substances comprising a transfer print. When making positive copies of documents, it is generally preferable to employ paper as the image support sheet.

The iluid processing reagent, photosensitive silver halide layer and the inner surface of the image support sheet may be so constituted as to effect the formation of a positive transfer image in terms of metallic silver or a dye or dyes. `In the preferred method illustrated, the fluid processing reagent is so constituted as to produce a silver image by a silver halide diffusion-transfer reversal process of the type wherein a soluble silver complex `is formed from undeveloped silver halide, is transferred and reduced to silver in an image-receptive layer. The positive silver image may be formed in or on the image support sheet, an image-receptive layer comprising or located on said image support sheet, or in the layer of fluid processing reagent itself. The fluid reagent may include, for example, a silver halide complexing agent and a thickening or film-forming agent and the image-receptive layer, which may comprise the layer of fluid processing reagent, contains materials providing silver precipitating nuclei. Processes 'of this type are well known to those skilled in the art and for further examples of these processes and materials useful therein, reference may be had to Patents Nos. 2,543,181, issued February 27, 19521, and 2,662,822, issued December l5, 1953, both n the name of Edwin H. Land.

In embodiments of the invention wherein it is desired to produce a positive transfer print in terms of a dye or dyes the image-forming material produced during processing in the photosensitive layer includes a color-providing substance. The expression color-providing substances, as used herein, is intended to include all types of substances or reagents which may be utilized to produce a positive image in terms of a dye, and may be initially contained in the photosensitive layer. These colorproviding substances may comprise dyes or intermediates for dyes and are not necessarily of the same color as the image dye to be produced, and may be of a dilerent color or a neutral hue. Such color-providing substances do not form part of the inventive subject matter of this application and therefore are not given in detail. For purposes of illustration, however, mention may be made of the following types of color-providing substances which may be utilized in employing inventive concepts of this invention:

(1) Color formers or couplers which react with the oxidation product of color developers to produce a dye; see for example the following patents issued to Edwin H. Land: 2,559,643, issued July 10, 1951, 2,661,293, issued December 1, 1953, 2,698,244, issued December 28, 1954, and 2,698,798, issued January 4, 1955.

(2) Self-coupling developers, e.g., a silver halide developing agent capable of coupling with itself, when oxidized, to form a dye; see for example the above-mentioned Patent No. 2,698,244.

(3) Dye developers, that is, complete dyes which possess a silver halide developing function; see for example the copending application of Howard G. Rogers, Serial No. 415,073, filed March 9, 1954 (now abandoned in favor of Serial No. 748,421, led July 14, 1958, now U.S. Patent No. 2,983,606, issued May 9, 1961).

(4) Leuco dyes, that is, dyes utilized in their leuco or reduced form and which, in said leuco form, possess a silver halide developing function but which must be oxidized after transfer to the image-receiving material; see for example the copending applicati-on of Howard G. Rogers, Serial No. 464,175, tiled October 22, 1954 (now abandoned in favor of Serial No. 765,925, filed October 8, 1958, now U. S. Patent No. 2,909,430, issued October 20, 1959).

(5 Coupling dyes, i.e., a complete dye which is capable of coupling with the oxidation product of a color developer, e.g., diethyl para-phenylenediamine, to form an immobile dye; see for example the copending application of Howard G. Rogers, Serial No. 358,012, filed May 28, 1953 (now U.S. Patent No. 2,774,668, issued December 18, 1956).

The fluid processing reagent may be supplied and distributed between photosensitive sheet 10 and image support sheet 42 by a variety of known methods and is preferably supplied in a rupturable container, such as is shown and described in the aforementioned Land Patent No. 2,543,181, and is spread from the container in a thin layer between the sheets by movement of the sheets in superposition between a pair of pressure-applying members. In the silver halide diffusion-transfer process illustrated, silver halide in areas 18a and 18h, rendered developable by exposure, is reduced to silver in situ and a soluble silver complex, formed from undeveloped silver halide in areas 18C underlying screen elements 14 and located opposite the dark areas of the original, is transferred by depthwise and controlled lateral diffusion to an image-receptive layer 46 on second sheet 42 where it is reduced to silver to form an image corresponding to the dark areas of the Original. The thicknesses of the silver halide emulsion layer and the layer of processing fluid in FIGURE 1, preferably, are predeterminedly controlled and related to one another so that there is lateral, as Well as depthwise, diffusion (designated by arrows) of the silver complex in order that silver from areas 18e` underlying screen elements 14 is deposited opposite areas 18a between the screen elements from which there is substantially no transfer of image-forming substances because of exposure thereof by the initial incident exposure. This lateral diffusion preferably amounts to approximately half the width of the screen openings or areas 18a, with the result that, where the boundary between light and dark areas of the original is located across the screen opening as illustrated, the location of the boundary of the transfer image corresponds substantially to that of the original. Since diffusion-transfer is proportional to exposure of the silver halide and the only silver halide which enters into the transfer processing is that which is located behind the screen elements and is exposed only to light reflected from the subject being copied, the method is useful for reproducing tones as well as dark, nonreflecting areas and light, reflecting areas.

It has been noted that lateral or sidewise diffusion of the image-forming component, whether it be, e.g., a soluble silver complex, a dye r a dye intermediate, is utilized to effect the reproduction of intermediate tones. This lateral diffusion preferably amounts to approximately half the width of the screen openings or areas 18a. It has been found that the desired lateral diffusion may be obtained if the photosensitive element and the image-receiving element are spaced apart a distance such that the thickness of the applied layer of processing fluid is approximately 4one-half the width of the screen openings. Thus, where the screen openings were approximately 0.006 in width, the desired lateral diffusion has been obtained by applying a processing fluid (containing approximately 3.5 to 4.5% sodium carboxymethyl cellulose) in a layer approximately 0.003 thick and imbibing for approximately one minute. It will be apparent that the particular thickness of the layer of processing fluid necessary to obtain the requisite lateral diffusion with a particular size screen opening may be readily determined by routine experimentation.

In addition, it should be noted that the amount of lateral diffusion should be such that the maximum density of the areas of the transfer image opposite the screen openings is preferably at least approximately 75% of the maximum density of the transfer image areas opposite the onamie screen areas 14.

It should be noted that lateral diffusion, normally undesired and vigorously minimized because of the attendant fuzziness or lack of sharpness in the transfer image, is deliberately effected in this invention in order to obtain the desired tone reproduction. It will be noted that the use of submacroscopic screen elements permits this intentional utilization of lateral diffusion while retaining satisfactory image sharpness.

It will also be noted that this invention utilizes normal, i.e., medium, contrast as well as low contrast emulsions7 in contradistinction to the conventional and normal requirement that high contrast emulsions be used in reflex copy processes. This also permits the use of emulsions having great sensitivity as well as broader or more desirable spectral sensitivity.

Photosensitive sheet 10 and second sheet 42 are maintained in superposition with layer 46 of the fluid processing reagent located therebetween during a processing period of predetermined duration, at the end of which the two sheets are stripped apart. In the form shown, fluid layer 46 contains a film-forming agent and is adapted to adhere to the photosensitive sheet when the transfer print comprising sheet 42 is stripped therefrom. In other processes of this type wherein the positive transfer image is formed in fluid layer 46, this layer is adapted to adhere to sheet 42 and may be subjected to a subsequent treatment for further hardening and/ or preserving the image-carrying layer.

A further modification of the process of the invention is possible employing a photosensitive sheet, similar in many respects to sheet 20, and including an image-receptive layer on, or comprising a part of a transparent support sheet 22 and located between sheet 22 and the screen. Exposure and processing of this type of photosensitive sheet would be accomplished substantially in the manner described except that the second sheet 42 would function only to aid in spreading and confining the fluid processing reagent, diffusion-transfer of image-forming substances being toward the image-receptive layer and away from the second sheet. The material comprising the screen elements would be so constituted that the emulsion and screen elements would be stripped, together with the layer of fluid, from support sheet 22 and the transfer image formed thereon. If a reflection print is desired, a translucent layer can be provided between the screen elements and the image-receptive layer so that the image-forming substances diffuse through this translucent layer which forms a dense white background for the positive transfer image.

Still another mechanism for forming transfer images may be embodied in the process of the invention to produce transfer prints in terms of dyes. In this method, the light-sensitive material of the photosensitive sheet comprises a layer of a light-hardenable colloid employed for controlling the imagewise diffusion-transfer of dyes to an image-receptive or dyeable layer. Basically, this mechanism of image formation involves the provision of a soluble dye in association with the layer of light-hardenable colloid, exposing the photosensitive material to effect an imagewise differential hardness or permeability of the photosensitive layer, and thereafter absorbing a processing liquid into at least the unexposed regions of the photosensitive layer and, by imbibition, transferring an imagewise distribution of the dye through the unexposed regions of this layer to an image-receptive lor dyeable layer superposed with the photosensitive layer. Photosensitive materials suitable for this purpose are well known in the art and incude, for example, dichromated colloids such as gelatin, and light-sensitive polymeric materials such as polyvinyl cinnamate whose permeability to solutions of certains dyes is decreased by exposure to actinic light. The use of light-sensitive polymeric materials such as polyvinyl cinnamate to control the diffusion transfer of a dye or dye intermediate is claimed in the copending application of Howard G. Rogers, Serial No. 94,521, filed March 9, 1961. The diffusion-transfer of dyes in this method is lateral as well as depthwise so that tones may be reproduced as well as complete blacks or colors.

While the photosensitive sheet has been shown as including minute areas rendered opaque or impervious to actinic light by elements of a screen, the screen arrangement yof minute, light-impervious areas may be provided by incorporating a suitable material in areas of the photosensitive material itself. For example, when the photosensitive material is a dichromated colloid or a lightpolymerizable material, a light-asborbing dye can be incorporated into the photosensitive material so that actinic light incident thereon from the source is absorbed and at least a surface portion of the photosensitive material, in contact with the subject being copied, is limited to being exposed substantially only by light reflected from the subject. This light-absorbing dye may itself comprise the dye which is transferred during processing to form the positive print.

In other modifications of the method of the invention and materials useful therein, the photosensitive material may comprise photosensitive ferric salts which, when photoexposed, are capable of being reduced to ferrous salts. Suitable ferrie salts are well known in the art and include, for example, ferric chloride and ferrie salts of organic acids such as ferric oxalate, ferrie tartrate and ferric citrate, The fluid processing agent would preferably include a coupler or at least be capable of activating a coupler which differentiates between ferric and ferrous salts to form transferable image-forming reduction products With unexposed ferric salts. Examples of such couplers include potassium ferricyanide, potassium ferrocyanide and the tannins. In still another modification of the invention, the photosensitive material may comprise photosensitive diazo compounds which, following exposure, may be treated with a liquid agent to produce diffusible image-forming components substantially only in unexposed areas of the photosensitive layer containing said diazo compounds.

While the process of the invention has been described with regard to the production of black and rwhite copies, it has equal utility for the production of copies in terms of dyes of different colors. Also, by the proper selection of sensitive emulsions and screen materials, the process may be utilized for making reflex copies ofsubject matter of only a certain predetermined color or colors, or, for example, for making positive color separation records.

Since certain changes may be made in the above process and product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

I1. A method of reflex copying comprising superposing a photosensitive sheet including a photosensitive material adapted, as a function of exposure thereof, to prevent diffusion transfer of an image-forming component, with the surface of a subject to be copied with said photosensitive material adjacent said surface, directing light, actinic to said photosensitive material, toward said sheet and onto an area thereof at least coextensive with the area of said surface to be copied, transmitting said actinic light through minute spaced-apart, submacroscopic areas of said sheet arranged in the form of a regular photographic screen pattern to said surface, and thereby fully exposing any photosensitive material opposite said minute areas, reflecting said actinic light from said surface toward said photosensitive material for exposing said photosensitive material provided in other minute spaced-apart, submacroscopic areas of said photosensitive sheet, said other areas being arranged in a screen pattern and Icomprising a substantial remaining portion of said area of said sheet and including the spaces between the first-mentioned minute areas on which said actinic light is incident, restricting said photosensitive material in said other areas to being exposed substantially only to said actinic light reflected from said surface, and thereafter superposing said photosensitive sheet with another sheet, distributing a fluid processing reagent containing a film-forming agent in a thin layer between said sheets to provide a layer having a thickness approximately one-half the width of the rst-mentioned minute areas, permeating said fiuid into said photosensitive material, forming diffusible, transferable image-forming components in said other minute areas and transferring, by diffusion, said diffusible imageforming components to an image-receiving layer superposed with said photosensitive material to form, in said image-receiving layer, an image which is a positive copy of said subject, said diffusion-transfer including, in addition to a depthwise diffusion from said photosensitive material to said image-receiving layer, a substantial predetermined lateral diffusion of said irnage-forming components from said other minute areas of said photosensitive material whereby a portion of said diliusible image-forming components is deposited in said image-receiving layer opposite said first-mentioned minute areas of said photosensitive material, said lateral diffusion being sufiicient to provide a substantially continuous tone transfer image.

2. The method of claim 1, wherein said photosensitive material is provided only in said other minute areas, exposure of said photosensitive material` by said incident actinic light being prevented -by an opaque layer posi- -tioned between said photosensitive material and a support therefor.

3. A method of reflex copying utilizing a photosensitive sheet including a light-transmitting support, a photosensitive layer including a silver halide emulsion and a regular photographic screen comprising first minute spaced-apart, submacroscopic areas for transmitting light actinic to said silver halide and second minute spacedapart, submacroscopic areas comprising the spaces between said first minute areas and being opaque to said actinic light, said first and second minute areas together comprising a substantial portion of said screen, which method comprises superposing said photosensitive sheet wit-h the surface of a subject to be copied with said photosensitive layer adjacent said surface, directing light actinic `to said photosensitive silver halide toward said sheet and onto an area thereof at least coextensive with the area of said subject to be copied, said screen being positioned between said emulsion and said actinic light, transmitting said actinic light through said support and said first minute areas of said screen to said surface, thereby fully exposing and rendering developable the areas of said photosensitive layer opposite said first minute areas of said screen, reflecting said actinic light from said surface toward said photosensitive layer thereby exposing said silver halide, located opposite said opaque second minute areas of said screen, substantially only by said actinic light reliected from said surface, and thereafter applying a processing solution thereby developing the exposed photosensitive silver halide, forming diffusible, transferable image-forming substances only in unexposed portions of said photosensitive layer opposite said opaque second minute areas of said screen as a function of said development, and transferring, by diffusion, said image-forming substances to another layer superposed with said photosensitive layer to form an image which is a substantially continuous tone positive copy of said subject, said processing fluid being applied to provide a layer having a thickness such that said diffusion-transfer provides, in addition to a depthwise diffusion, a lateral diffusion of said diffusible image-forming substances from each portion of said photosensitive layer located opposite one of said second minute areas of said screen approximately half the `distance to adjoining se-cond minute areas thereby depositing said image-forming substances in said other layer opposite said first minute areas of said screen, the maximum density of the areas of said transfer image opposite said first minute areas of said screen being at least approximately of the maximum density of the areas of said transfer image opposite said second minute areas of said screen.

4. The method of claim 3, wherein said photosensitive layer comprises silver halide, said transfer image comprises silver, said diffusible image-forming component is a solu'ble complex formed with undeveloped silver halide, and said transfer image is formed by precipitation of said silver from a solution of said complex.

5. The method of claim 3, wherein said photosensitive layer comprises silver halide, said transfer image comprises a dye and said ditfusible image-forming components include at least an intermediate for said dye, and said image-forming components are immobilized in exposed portions of said photosensitive layer by development of said silver halide.

6. The method of claim 3, wherein said uid is distributed in a thin layer on said photosensitive layer and said layer of fluid comprises said image-receiving layer in which said ditfusible image-forming components are deposited to form said transfer image.

References Cited by the Examiner UNITED STATES PATENTS 12 2,647,056 7/ 1953 Land 96-29 2,653,527 9/1953 Land 96-29 2,917,385 12/1959 Byrne 96-1 2,968,554 1/1961 Land.

3,010,391 11/1961 'Buskes et al. 96-28 3,019,124 1/1962 Rogers 117-8 FOREIGN PATENTS 614,155 12/1948 Great Britain. 761,495 11/1956 Great Britain. 59,365 5 1947 Netherlands.

OTHER REFERENCES The Photographic Journal, volume 90A, January 1950; pp. 7-15.

Rapid Ultra Rapid Gevacopy: pp. 1-23, April 15, 1957.

Vander Grinten, The Photographic Journal, September 1938, pp. 579-583. o

NORMAN G. TORCHIN, Primary Examiner.

HAROLD N. BURSTEIN, Examiner. 

1. A METHOD OF REFLEX COPYING COMPRISING SUPERPOSING A PHOTOSENSITIVE SHEET INCLUDING A PHOTOSENSITIVE MATERIAL ADAPTED, AS A FUNCTION OF EXPOSURE THEREOF, TO PREVENT DIFFUSION TRANSFER OF AN IMAGE-FORMING COMPONENT, WITH THE SURFACE OF A SUBJECT TO BE COPIED WITH SAID PHOTOSENSITIVE MATERIAL ADJACENT SAID SURFACE, DIRECTING LIGHT, ACTINIC TO SAID PHOTOSENSITIVE MATERIAL, TOWARD SAID SHEET AND ONTO AN AREA THEREOF AT LEAST COEXTENSIVE WITH THE AREA OF SAID SURFACE TO BE COPIED, TRANSMITTING SAID ACTININC LIGHT THROUGH MINUTE SPACED-APART, SUBMACROSCOPIC AREAS OF SAID SHEET ARRANGED IN THE FORM OF A REGULAR PHOTOGRAPHIC SCREEN PATTERN TO SAID SURFACE, AND THEREBY FULLY EXPOSING ANY PHOTOSENSITIVE MATERIAL OPPOSITE SAID MINUTE AREAS REFLECTING SAID ACTINIC LIGHT FROM SAID SURFACE TOWARD SAID PHOTOSENSITIVE MATERIAL FOR EXPOSING SAID PHOTOSENSITIVE MATERIAL PROVIDED IN OTHER MINUTE SPACED-APART, SUBMACROSCOPIC AREAS OF SAID PHOTOSENSITIVE SHEET, SAID OTHER AREAS BEING ARRANGED IN A SCREEN PATTERN AND COMPRISING A SUBSTANTIAL REMAINING PORTION OF SAID AREA OF SAID SHEET AND INCLUDING THE SPACES BETWEEN THE FIRST-MENTIONED MINUTE AREAS ON WHICH SAID ACTINIC LIGHT IS INCIDENT, RESTRICTING SAID PHOTOSENSITIVE MATERIAL IN SAID OTHER AREAS TO BEING EXPOSED SUBSTANTIALLY ONLY TO SAID ACTINIC LIGHT REFLECTED FROM SAID SURFACE, AND THEREAFTER SUPERPOSING SAID PHOTOSENSITIVE SHEET WITH ANOTHER SHEET, DISTRIBUTING A FLUID PROCESSING REAGENT CONTAINING A FILM-FORMING AGENT IN A THIN LAYER BETWEEN SAID SHEETS TO PROVIDE A LAYER 